Coherent light generators – Particular temperature control – Heat sink
Reexamination Certificate
2003-04-03
2004-12-07
Leung, Quyen (Department: 2828)
Coherent light generators
Particular temperature control
Heat sink
C372S043010
Reexamination Certificate
active
06829266
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical semiconductor device which packages or contains an optical semiconductor element therein, and more particularly to an optical semiconductor device which allows an increase in productivity thereof through a possible simplification to assembling processes, and a method of fabricating the same.
All of patents, patent applications, patent publications, scientific articles and the like, which will hereinafter be cited or identified in the present application, will, hereby, be incorporated by references in their entirety in order to describe more fully the state of the art, to which the present invention pertains.
2. Description of the Related Art
One of the typical optical semiconductor devices is a semiconductor laser device, which has such a structure as packaging a laser diode which is supplied with a current through leads for allowing the laser diode to emit a laser beam.
FIG. 1
is a schematic perspective view illustrative of a conventional general structure of a semiconductor laser device. The semiconductor laser device includes a stem
201
having an upper surface united with a post
202
, and a plurality of lead
204
, which penetrate the stem
201
and are separated by insulation materials
203
from the stem
201
, as well as a laser diode LD mounted on one side face of the post
202
and a photo-diode PD mounted on a part of the upper surface of the stem
201
.
The laser diode LD and the photo-diode PD are mounted thereon by die-bonding processes. The united structure of the stem
201
and the post
202
may be formed by processing a metal material. Each of the plural leads
204
is electrically connected through a metal wiring
205
to either one of the laser diode LD and the photo-diode PD. The laser diode LD is also electrically connected through the metal wiring
205
to the post
202
or indirectly connected to the stem
201
. The semiconductor laser device also includes a cap
206
placed on the upper surface of the stem
201
for covering the above elements mounted over the upper surface of the stem
201
. The stem
201
has a generally disk-like shape. The cap
206
has a generally cylinder shape. A periphery of the cap
206
is fusion-spliced with the stem
201
. The cap
206
also has a circular-shaped opening window. The metal wirings
205
are provided by a wire bonding process.
The united structure of the stem
201
and the post
202
may be formed by a machining or cutting process for a metal material or by welding the post
202
to the stem
201
. Since the stem
201
is made of the metal material, it is necessary to provide the insulating material
203
which electrically isolates the each lead
204
from the stem
201
, wherein the each lead
204
is supported via the insulating material
203
to the stem
201
. There are many fabrication steps for forming the stem assembly. This makes it difficult to realize desired batch-fabrication processes for processing and assembling plural semiconductor laser devices concurrently. This provides bars to realize desired cost reduction and to improve the accuracy in dimension of the device.
It is further necessary to mount the laser diode LD and the photo-diode PD on the stem assembly, for which purposes, the stem assembly is subjected to the die-bonding process, the wire-bonding process and the fusion-splicing process. In each of those process, the stem assembly is loaded into and unloaded from as well as positioned in each of equipments for taking place those processes. Those processes lower the productivity and make it difficult to realize the desired cost reduction. Lowering the accuracy in positioning of the stem assembly in the equipment causes lowering respective accuracy in the die-bonding process and the wire-bonding process, thereby making it difficult to obtain a high quality semiconductor laser device.
FIG. 2
is a schematic perspective view illustrative of another conventional structure of a semiconductor laser device disclosed in Japanese laid-open patent publication 2001-77262. This conventional technique is to simplify the fabrication processes for the stem assembly. The semiconductor laser device includes a stem
301
which further comprises a cylindrically shaped body
302
with a top narrow rim, a flange
303
united with a bottom peripheral edge of the cylindrically shaped body
302
, and an extension strip extending from an inside peripheral edge of the top narrow rim of the cylindrically shaped body
302
, wherein the extension strip
304
is bent at a right angle, so that a top of the extension strip extends in a vertical direction to form a vertical plate or a vertical wall which serves as a mount
304
. This stem
301
may be formed by a press working from a metal sheet or a metal plate. Further, an insulating material
305
such as a resin material is filled into an inner space of the cylindrically shaped body
302
. Plural leads
306
penetrate the insulating material
305
, so that the plural leads
306
are supported by the insulating material
305
and electrically separated from the stem
301
by the insulating material
305
. A submount
307
is attached onto the mount
304
. A laser diode LD and a photodiode PD are mounted on the sub-mount
307
. The laser diode LD and the photo-diode PD are electrically connected by a wire-bonding process through metal wirings
308
to the leads
306
.
This conventional technique shown in
FIG. 2
is advantageous as compared to the above-described conventional technique shown in
FIG. 1
in view of simplifying the fabrication processes for the stem and improving the dimensional accuracy of the device. Further, a cap is attached to the stem
301
by the fusion-splicing process, even the illustration of the cap is not omitted in FIG.
2
.
Accordingly, the conventional technique shown in
FIG. 2
still need the die-bonding process, the wire-bonding process and the fusion-splicing process. In each of those process, the stem assembly is loaded into and unloaded from as well as positioned in each of equipments for taking place those processes. Those processes lower the productivity and make it difficult to realize the desired cost reduction. Lowering the accuracy in positioning of the stem assembly in the equipment causes lowering respective accuracy in the die-bonding process and the wire-bonding process, thereby making it difficult to obtain a high quality semiconductor laser device.
FIG. 3
is a schematic perspective view illustrative of still another conventional structure of a semiconductor laser device disclosed in Japanese laid-open patent publication 2001-68778. Plural leads
301
comprising lead frames are encapsulated with a resin package
302
which has a generally thin box-shape. A sub-mount
303
is provided on a part of one of the leads
301
. A photo-diode PD and a laser diode LD are mounted on the sub-mount
303
. The photo-diode PD and the laser diode LD are further electrically connected to other ones of the leads
301
through flexible wirings
304
. Each of the lead frames may be formed by a press working from a metal sheet or a metal plate. This simplifies the fabrication processes and allows arty improvement in the dimensional accuracy of the lead frames. In this case, the package
302
should have a flat-box-shape as shown in FIG.
3
. It is, however, difficult to realize this conventional technique by a can-shaped or cylinder-shaped semiconductor laser device as shown in
FIGS. 1 and 2
. This flat-box-shaped semiconductor laser device as shown in
FIG. 3
is inferior in heat radiation capability as compared to the above-described cylinder-shaped semiconductor laser device as shown in
FIGS. 1 and 2
. This conventional technique is not applicable to any optical devices including the cylinder-shaped semiconductor laser. It is necessary for applying this conventional technique to change in design of the device.
In the above circumstances, the development of a novel optical semiconductor device free from the above problems is desirable.
Hirasawa Koki
Uchida Kenji
Hayes & Soloway P.C.
Leung Quyen
NEC Compound Semiconductor Devices Ltd.
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